The objectives of this research are: (i) validation of in-vivo animation of event-related gamma-oscillations on electrocorticography (ECoG) as a language mapping method for children who undergo brain surgeries, and (ii) better understanding of the human language system. About 1% of the general population has epilepsy; one-fifth of epilepsy in children is medically intractable; subsets of children with intractable focal epilepsy benefit from surgical resection of the epileptogenic zone. Brain tumor is often associated with focal epilepsy in children, and surgical resection of tumor together with the epileptogenic focus is indicated in such children. The goals of both epilepsy and brain tumor surgeries include identification and preservation of the eloquent cortices such as the language cortex. However, conventional brain mapping using electrical stimulation lacks sufficient sensitivity to identify the language areas in children under age 10 years, often takes several hours to complete, and has a risk of stimulation-induced seizures. Thus, alternative language mapping techniques would be highly desirable in these children. We have recently developed a novel language mapping method which we refer to as in-vivo animation of event-related gamma-oscillations. This new and innovative method appears promising for language mapping in children. As the next step, we will validate this mapping method using electrical stimulation and postoperative neuropsychological testing in this project. Specifically, we will determine whether brief auditory-language tasks will successively delineate gamma augmentation in the cortical sites responsible for receptive language function, expressive language function and overt speech. We will also determine whether a visual-language task will successively delineate gamma augmentation in the cortical sites responsible for receptive language function and expressive language function. Innovation in our project includes: (i) the study focusing on young subjects across a wide range of age (5 - 20 years), in about 40% of whom identification of the language cortex is difficult using electrical stimulation, (ii) in-vivo animation of cortical activation on an individual three-dimensional MRI with a good temporal resolution [10 msec] and a good spatial resolution [1 cm], and (iii) assessment of ECoG signals least affected by artifacts derived from overt speech tasks. This project is clinically significant since the results will be directly translatable into patient management and our event-related ECoG analysis has the potential to become a mainstream language mapping method which is less-invasive, more time-efficient, and more patient-friendly compared to the currently used electrical stimulation method.